Field of the Invention
The present invention relates generally to fire suppression sprinklers. More particularly, the present invention relates to heat-sensitive trigger for a fire sprinkler valve or head.
Related Art
Fire sprinkler valves are used in fire suppression systems for buildings or facilities. Such fire sprinkler valves have a plug retained by a heat sensitive trigger. Prior art fire sprinkler valves use triggers that are generally of two types: 1) older mechanical linkage triggers; and 2) newer frangible bulb triggers. The older mechanical linkage triggers used an offset linkage or a spring loaded linkage held in place by an alloy that melts at a low temperature, releasing the linkage, and thus the plug. The newer frangible bulb triggers use a glass bulb filled with a liquid that expands when heated, bursting the glass bulb, and releasing the trigger. The trigger mechanism is usually held between a yoke or frame and the plug. For example, see U.S. Pat. No. 5,967,238 and U.S. Pat. No. 4,796,710. The glass bulbs, however, can sustain hairline fractures during shipping; resulting in leakage of the liquid. In addition, the liquid in the bulb can be colored to correspond to a head rating of the bulb, i.e. the heat at which the bulb bursts, activating the sprinkler. The color in the liquid, however, can fade in UV light and cold temperatures. Thus, the fire sprinkler valves with a bulb type trigger have a limited life expectancy of 25 years and should be inspected regularly. The older style fire sprinkler valves with a linkage type trigger have a life expectancy of 50 years.